The invention relates to a device for connecting the ends of steel pipes by means of orbital welding.
In particular, the invention relates to the welding of pipes, which may for example have wall thicknesses of 2 to 20 mm and a diameter of 60 to 1600 mm and which are connected to each other to form pipe lines by means of different welding procedures such as laser beam welding, combined laser beam/laser arc welding or electric arc welding. In the following, pipes are understood as circular pipes as well as hollow profiles with different cross sections.
The orbital welding of pipes is generally known for example from DE 103 34 446 A1. Here an orbital welding device for connecting two pipe ends is disclosed, wherein the device is attached and clamped to a first pipe end and the second pipe end is brought into welding position in so as to confront the first pipe end. By means of two welding heads which are offset relative to each other by 180° and which are guided pivotal about an axis, a 360° circular welding seam can be achieved. A disadvantage is that two welding heads are required in order to weld the pipe along the entire circumference.
A further orbital welding device is known from WO 2005/0-56230 A1 in which a combination of metal protective gas welding and laser arc welding is used. This so called laser MSG hybrid welding is characterized in that the electric arc and the laser beam are arranged at a defined distance to ach other and a higher gap bridging capacity can be achieved compared to a pure laser beam welding process. The device includes a guide ring, which can be oriented relative to the end of the first pipe. The orientation occurs via multiple clamping screws, which are arranged along the guide ring circumference and by means of which the distance of the guide ring to the pipe surface can be adjusted. The guide ring serves for guiding an orbital carriage, which can be moved thereon and which can accommodate further components for process monitoring and welding seam checking. The described device is used in mobile application for orbital welding of pipes to pipelines.
A disadvantage of this device is the complex construction with guide rings that are closed about the pipe and the elaborate alignment and centering of the pipe ends. Especially the centering requires great effort in the case of large pipe diameters and requires additional centering devices in the device having correspondingly great holding forces in order to ensure a geometrically stable welding groove during the welding. This makes the device very heavy and it can its use in mobile application is very difficult.
In addition the sequence of the welding process is very complex in which the pipe ends have to be inserted into the device and centered and subsequently the welded pipe has to be moved lengthwise out of the device.
In summary, no industrially applicable orbital guiding system exists in the state of the art that is optimally adjusted to the demands regarding quality and economical efficiency of the orbital welding.